Cladding of alloys using flux and metal powder cored feed material

ABSTRACT

A metal cladding process utilizing a feed material ( 66 ) formed as a hollow sheath ( 68 ) containing a powdered core ( 70 ) including powdered metal and powdered flux material. The powdered metal and flux may have overlapping mesh size ranges. The sheath may be an extrudable subset of elements of a desired superalloy cladding material, with the powdered metal and powdered flux materials complementing the sheath to form the desired superalloy material when melted. The powdered metal may include an excess of titanium to compensate for a reaction of titanium with oxygen or carbon dioxide in a shielding gas. Heat for melting may be provided by an energy beam ( 64 ) or by utilizing the feed material as an electrode in a cold metal arc welding torch ( 54 ).

FIELD OF THE INVENTION

This invention relates generally to the field of metals joining, andmore particularly to the welding clad buildup and repair of materialsusing a hollow cored feed material containing powdered flux and powderedmetal.

BACKGROUND OF THE INVENTION

Welding processes vary considerably depending upon the type of materialbeing welded. Some materials are more easily welded under a variety ofconditions, while other materials require special processes in order toachieve a structurally sound joint without degrading the surroundingsubstrate material.

Common arc welding generally utilizes a consumable electrode as the feedmaterial. In order to provide protection from the atmosphere for themolten material in the weld pool, an inert cover gas or a flux materialmay be used when welding many alloys including, e.g. steels, stainlesssteels, and nickel based alloys. Inert and combined inert and active gasprocesses include gas tungsten arc welding (GTAW) (also known astungsten inert gas (TIG)) and gas metal arc welding (GMAW) (also knownas metal inert gas (MIG) and metal active gas (MAG)). Flux protectedprocesses include submerged arc welding (SAW) where flux is commonlyfed, flux cored arc welding (FCAW) where the flux is included in thecore of the electrode and shielded metal arc welding (SMAW) where theflux is coated on the outside of the filler electrode.

The use of energy beams as a heat source for welding is also known. Forexample, laser energy has been used to melt pre-placed stainless steelpowder onto a carbon steel substrate with powdered flux materialproviding shielding of the melt pool. The flux powder may be mixed withthe stainless steel powder or applied as a separate covering layer. Tothe knowledge of the inventors, flux materials have not been used whenwelding superalloy materials.

It is recognized that superalloy materials are among the most difficultmaterials to weld due to their susceptibility to weld solidificationcracking and strain age cracking. The term “superalloy” is used hereinas it is commonly used in the art; i.e., a highly corrosion andoxidation resistant alloy that exhibits excellent mechanical strengthand resistance to creep at high temperatures. Superalloys typicallyinclude a high nickel or cobalt content. Examples of superalloys includealloys sold under the trademarks and brand names Hastelloy, Inconelalloys (e.g. IN 738, IN 792, IN 939), Rene alloys (e.g. Rene N5, Rene80, Rene 142), Haynes alloys, Mar M, CM 247, CM 247 LC, C263, 718,X-750, ECY 768, 282, X45, PWA 1483 and CMSX (e.g. CMSX-4) single crystalalloys.

Weld repair of some superalloy materials has been accomplishedsuccessfully by preheating the material to a very high temperature (forexample to above 1600° F. or 870° C.) in order to significantly increasethe ductility of the material during the repair. This technique isreferred to as hot box welding or superalloy welding at elevatedtemperature (SWET) weld repair, and it is commonly accomplished using amanual GTAW process. However, hot box welding is limited by thedifficulty of maintaining a uniform component process surfacetemperature and the difficulty of maintaining complete inert gasshielding, as well as by physical difficulties imposed on the operatorworking in the proximity of a component at such extreme temperatures.

Some superalloy material welding applications can be performed using achill plate to limit the heating of the substrate material; therebylimiting the occurrence of substrate heat affects and stresses causingcracking problems. However, this technique is not practical for manyrepair applications where the geometry of the parts does not facilitatethe use of a chill plate.

FIG. 6 is a conventional chart illustrating the relative weldability ofvarious alloys as a function of their aluminum and titanium content.Alloys such as Inconel® 718 which have relatively lower concentrationsof these elements, and consequentially relatively lower gamma primecontent, are considered relatively weldable, although such welding isgenerally limited to low stress regions of a component. Alloys such asInconel® 939 which have relatively higher concentrations of theseelements are generally not considered to be weldable, or can be weldedonly with the special procedures discussed above which increase thetemperature/ductility of the material and which minimize the heat inputof the process. For purposes of discussion herein, a dashed line 80indicates a border between a zone of weldability below the line 80 and azone of non-weldability above the line 80. The line 80 intersects 3 wt.% aluminum on the vertical axis and 6 wt. % titanium on the horizontalaxis. Within the zone of non-weldability, the alloys with the highestaluminum content are generally found to be the most difficult to weld.

It is also known to utilize selective laser melting (SLM) or selectivelaser sintering (SLS) to melt a thin layer of superalloy powderparticles onto a superalloy substrate. The melt pool is shielded fromthe atmosphere by applying an inert gas, such as argon, during the laserheating. These processes tend to trap the oxides (e.g. aluminum andchromium oxides) that are adherent on the surface of the particleswithin the layer of deposited material, resulting in porosity,inclusions and other defects associated with the trapped oxides. Postprocess hot isostatic pressing (HIP) is often used to collapse thesevoids, inclusions and cracks in order to improve the properties of thedeposited coating.

For some superalloy materials in the zone of non-weldability there is noknown acceptable welding or repair process. Furthermore, as new andhigher alloy content superalloys continue to be developed, the challengeto develop commercially feasible joining processes for superalloymaterials continues to grow.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in the following description in view of thedrawings that show:

FIG. 1 illustrates a cladding process using a multi-layer powder.

FIG. 2 illustrates a cladding process using a mixed layer powder.

FIG. 3 illustrates a cladding process using a cored filler wire and acold metal arc welding torch.

FIG. 4 illustrates a cladding process using a cored filler wire and anenergy beam.

FIG. 5 illustrates an energy beam overlap pattern.

FIG. 6 is a prior art chart illustrating the relative weldability ofvarious superalloys.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have developed a cladding process that can be usedsuccessfully to deposit the most difficult to weld superalloy materials.While flux materials have not previously been utilized when weldingsuperalloy materials, embodiments of the inventive processadvantageously utilize a powdered flux material during a melting andre-solidifying process. Some embodiments also utilize the precise energyinput control capability of energy beam heating processes, such as laserbeam heating. The powdered flux material is effective to provide beamenergy trapping, impurity cleansing, atmospheric shielding, beadshaping, and cooling temperature control in order to accomplishcrack-free joining of superalloy materials without the necessity forhigh temperature hot box welding or the use of a chill plate or the useof inert shielding gas. While various elements of the present inventionhave been known in the welding industry for decades, the presentinventors have innovatively developed a combination of steps for asuperalloy cladding process that solves the long-standing problem ofcracking of these materials.

FIG. 1 illustrates a process where a layer of cladding 10 of asuperalloy material is being deposited onto a superalloy substratematerial 12 at ambient room temperature without any preheating of thesubstrate material 12 or the use of a chill plate. The substratematerial 12 may form part of a gas turbine engine blade, for example,and the cladding process may be part of a repair procedure in someembodiments. A layer of granulated powder 14 is preplaced on thesubstrate 12, and a laser beam 16 is traversed across the layer ofpowder 14 to melt the powder and to form the layer of cladding 10covered by a layer of slag 18. The cladding 10 and slag 18 are formedfrom the layer of powder 14 which includes a layer of powderedsuperalloy material 20 covered by a layer of powdered flux material 22.

The flux material 22 and resultant layer of slag 18 provide a number offunctions that are beneficial for preventing cracking of the cladding 10and the underlying substrate material 12. First, they function to shieldboth the region of molten material and the solidified (but still hot)cladding material 10 from the atmosphere in the region downstream of thelaser beam 16. The slag floats to the surface to separate the molten orhot metal from the atmosphere, and the flux may be formulated to producea shielding gas in some embodiments, thereby avoiding or minimizing theuse of expensive inert gas. Second, the slag 18 acts as a blanket thatallows the solidified material to cool slowly and evenly, therebyreducing residual stresses that can contribute to post weld reheat orstrain age cracking. Third, the slag 18 helps to shape the pool ofmolten metal to keep it close to a desired ⅓ height/width ratio. Fourth,the flux material 22 provides a cleansing effect for removing traceimpurities such as sulfur and phosphorous that contribute to weldsolidification cracking. Such cleansing includes deoxidation of themetal powder. Because the flux powder is in intimate contact with themetal powder, it is especially effective in accomplishing this function.Finally, the flux material 22 may provide an energy absorption andtrapping function to more effectively convert the laser beam 16 intoheat energy, thus facilitating a precise control of heat input, such aswithin 1-2%, and a resultant tight control of material temperatureduring the process. Additionally, the flux may be formulated tocompensate for loss of volatized elements during processing or toactively contribute elements to the deposit that are not otherwiseprovided by the metal powder itself. Together, these process stepsproduce crack-free deposits of superalloy cladding on superalloysubstrates at room temperature for materials that heretofore werebelieved only to be joinable with a hot box process or through the useof a chill plate.

FIG. 2 illustrates another embodiment where a layer of cladding 30 of asuperalloy material is being deposited onto a superalloy substratematerial 32, which in this embodiment is illustrated as a directionallysolidified material having a plurality of columnar grains 34. In thisembodiment, the layer of powder 36 is pre-placed or fed onto the surfaceof the substrate material 32 as a homogeneous layer including a mixtureof both powdered alloy material 38 and powdered flux material 40. Thelayer of powder 36 may be one to several millimeters in thickness insome embodiments rather than the fraction of a millimeter typical withknown selective laser melting and sintering processes. Typical powderedprior art flux materials have particle sizes ranging from 0.5-2 mm, forexample. However, the powdered alloy material 38 may have a particlesize range (mesh size range) of from 0.02-0.04 mm or 0.02-0.08 mm orother sub-range therein. This difference in mesh size range may workwell in the embodiment of FIG. 1 where the materials constitute separatelayers; however, in the embodiment of FIG. 2, it may be advantageous forthe powdered alloy material 38 and the powdered flux material 40 to haveoverlapping mesh size ranges, or to have the same mesh size range inorder to facilitate mixing and feeding of the powders and to provideimproved flux coverage during the melting process.

The energy beam 42 in the embodiment of FIG. 2 is a diode laser beamhaving a generally rectangular cross-sectional shape, although otherknown types of energy beams may be used, such as electron beam, plasmabeam, one or more circular laser beams, a scanned laser beam (scannedone, two or three dimensionally), an integrated laser beam, etc. Therectangular shape may be particularly advantageous for embodimentshaving a relatively large area to be clad, such as for repairing the tipof a gas turbine engine blade. The broad area beam produced by a diodelaser helps to reduce weld heat input, heat affected zone, dilution fromthe substrate and residual stresses, all of which reduce the tendencyfor the cracking effects normally associated with superalloy repair.Optical conditions and hardware optics used to generate a broad arealaser exposure may include but are not limited to: defocusing of thelaser beam; use of diode lasers that generate rectangular energy sourcesat focus; use of integrating optics such as segmented mirrors togenerate rectangular energy sources at focus; scanning (rastering) ofthe laser beam in one or more dimensions; and the use of focusing opticsof variable beam diameter (e.g. 0.5 mm at focus for fine detailed workvaried to 2.0 mm at focus for less detailed work). The motion of theoptics and/or substrate may be programmed as in a selective lasermelting or sintering process to build a custom shape layer deposit.Advantages of this process over known laser melting or sinteringprocesses include: high deposition rates and thick deposit in eachprocessing layer; improved shielding that extends over the hot depositedmetal without the need for inert gas; flux will enhance cleansing of thedeposit of constituents that otherwise lead to solidification cracking;flux will enhance laser beam absorption and minimize reflection back toprocessing equipment; slag formation will shape and support the deposit,preserve heat and slow the cooling rate, thereby reducing residualstresses that otherwise contribute to strain age (reheat) crackingduring post weld heat treatments; flux may compensate for elementallosses or add alloying elements; and powder and flux preplacement orfeeding can efficiently be conducted selectively because the thicknessof the deposit greatly reduces the time involved in total part building.

The embodiment of FIG. 2 also illustrates the use of a base alloy feedmaterial 44 (alternatively referred to as a filler material). The feedmaterial 44 may be in the form of a wire or strip that is fed oroscillated toward the substrate 32 and is melted by the energy beam 42to contribute to the melt pool. If desired, the feed material may bepreheated (e.g. electrically) to reduce overall energy required from thelaser beam. While it is difficult or impossible to form some superalloymaterials into wire or strip form, materials such as pure nickel ornickel-chromium or nickel-chromium-cobalt are readily available in thoseforms. In the embodiment of FIG. 2, the base alloy feed material 44,powdered alloy material 38 and powdered flux material 40 areadvantageously selected such that the layer of cladding material 30 hasthe composition of a desired superalloy material. The filler materialmay be only an extrudable subset of elements of a composition ofelements defining a desired superalloy material, and the powdered metalmaterial includes elements that complement the elements in the fillermaterial to complete the composition of elements defining the desiredsuperalloy material. The filler material and the powdered metal materialare combined in the melt pool to form the repaired surface of desiredsuperalloy material 30. As in FIG. 1, the process produces a layer ofslag 46 that protects, shapes and thermally insulates the layer ofcladding material 30.

FIG. 3 illustrates an embodiment where a layer of superalloy material 50is deposited onto a superalloy substrate 52 using a cold metal arcwelding torch 54. The torch 54 is used to feed and to melt a fillermaterial 56 having the form of a cored wire or strip material includinga hollow metal sheath 57 filled with a powdered core material 59. Thepowdered core material 59 may include powdered metal alloy and/or fluxmaterials. Advantageously, the metal sheath 57 is formed of a materialthat can be conveniently formed into a hollow shape, such as nickel ornickel-chromium or nickel-chromium-cobalt, and the powdered material 59is selected such that a desired superalloy composition is formed whenthe filler material 56 is melted. The sheath contains sufficient nickel(or cobalt) to achieve the desired superalloy composition, thus thesolid to solid ratio of sheath verses powdered core material may bemaintained at a ratio of 3:2, for example. The heat of the arc melts thefiller material 56 and forms a layer of the desired superalloy material50 covered by a layer of slag 58. Powdered flux material may be providedin the filler material 56 (for example 25% of the core volume) or it maybe pre-placed or deposited onto the surface of the substrate 52 (notshown—see FIG. 2), or the electrode may be coated with flux material, orany combination of these alternatives. A supplemental powdered metalmaterial may also be added to the melt pool (not shown—see FIGS. 1 and2) by being pre-placed on the surface of the substrate 52 or by beingdirectly fed into the melt pool during the step of melting. In variousembodiments, the flux may be electrically conductive (electroslag) ornot (submerged arc), and it may be chemically neutral or additive. Asbefore, the filler material may be preheated to reduce process energyrequired—in this case from the cold metal arc torch. The use of fluxwould provide shielding thereby reducing or eliminating the need forinert or partially inert gas commonly required in the cold metal arcprocess.

FIG. 4 illustrates an embodiment where a layer of superalloy material 60is deposited onto a superalloy substrate 62 using an energy beam such aslaser beam 64 to melt a filler material 66. As described above withrespect to FIG. 3, the filler material 66 includes a metal sheath 68that is constructed of a material that can be conveniently formed into ahollow shape, such as nickel or nickel-chromium ornickel-chromium-cobalt, and a powdered material 70 is selected such thata desired superalloy composition is formed when the filler material 66is melted by the laser beam 64. The powdered material 70 may includepowdered flux as well as alloying elements. The heat of the laser beam64 melts the filler material 66 and forms a layer of the desiredsuperalloy material 60 covered by a layer of slag 72. As before, thefiller material may be preheated, such as with an electrical current, toreduce process energy required—in this case from the laser beam.

One embodiment of a filler material 56, 66 is formulated to depositalloy 247 material as follows:

-   -   sheath solid volume is about 60% of total metallic solid volume        and is pure Ni;    -   core metal powder volume is about 40% of total metallic solid        volume including sufficient Cr, Co, Mo, W, Al, Ti, Ta, C, B, Zr        and Hf; that when melted together and mixed with the pure nickel        from the sheath, produces alloy 247 composition of nominal        weight percent 8.3 Cr, 10 Co, 0.7 Mo, 10 W, 5.5 Al, 1 Ti, 3 Ta,        0.14 C, 0.015 B, 0.05 Zr and 1.5 Hf; and    -   core flux powder volume represents additional, largely        non-metallic, wire volume possibly about equal in size to the        metal powder volume and includes alumina, fluorides and        silicates in a 35/30/35 ratio. The mesh size range of the flux        is such as to distribute uniformly within the core metal powder.

For embodiments where the heat of melting is provided by an arc, it iscommon to provide oxygen or carbon dioxide in the flux or shielding gasin order to maintain arc stability. However, the oxygen or carbondioxide will react with titanium and some of the titanium will be lostas vapor or oxides during the melting process. The present inventionallows the amount of titanium included in the filler material to be inexcess of the amount of titanium desired in the deposited superalloycomposition to compensate for this loss. For the example of alloy 247described above, the amount of titanium included in the core metalpowder may be increased from 1% to 3%.

One will appreciate that other alloys, such as stainless steels forexample, may be deposited with a similar process where a cored feedmaterial is filled with a powdered core material including powdered fluxand powdered metal. The powdered metal may be used to augment thecomposition of the sheath material to obtain a cladding material of adesired chemistry. For embodiments where there is a loss of material dueto vaporization during the melting step, the powdered metal may includean excess of the lost material to compensate for the loss. For example,when alloy 321 stainless steel sheath material is deposited under ashielding gas containing oxygen or carbon dioxide, some of the titaniumfrom the sheath material is lost due to reaction with the oxygen orcarbon dioxide. The powdered core material in such an embodiment mayinclude powdered flux and powdered titanium to compensate for the loss,thus providing a desired alloy 321 cladding composition.

Repair processes for superalloy materials may include preparing thesuperalloy material surface to be repaired by grinding as desired toremove defects, cleaning the surface, then pre-placing or feeding alayer of powdered material containing flux material onto the surface,then traversing an energy beam across the surface to melt the powder andan upper layer of the surface into a melt pool having a floating slaglayer, then allowing the melt pool and slag to solidify. The meltingfunctions to heal any surface defects at the surface of the substrate,leaving a renewed surface upon removal of the slag typically by knownmechanical and/or chemical processes. The powdered material may be onlyflux material, or for embodiments where a layer of superalloy claddingmaterial is desired, the powdered material may contain metal powder,either as a separate layer placed under a layer of powdered fluxmaterial, or mixed with the powdered flux material, or combined with theflux material into composite particles, such the melting forms the layerof cladding material on the surface. Optionally, a feed material may beintroduced into the melt pool in the form of a strip or wire. Thepowdered metal and feed material (if any), as well as any metalcontribution from the flux material which may be neutral or additive,are combined in the melt pool to produce a cladding layer having thecomposition of a desired superalloy material. In some embodiments, afeed material of nickel, nickel-chromium, nickel-chromium-cobalt orother conveniently extruded metal is combined with appropriate alloyingmetal powders to produce the desired superalloy composition in thecladding, thereby avoiding the problem of forming the desired superalloymaterial into a wire or strip form.

While pre-heating of the substrate is not necessarily required to obtainacceptable results, it may be desired to apply heat to the superalloysubstrate and/or to the feed material and/or the powder prior to themelting step in some embodiments, such as to increase the ductility ofthe substrate material and/or to reduce beam energy otherwise requiredto melt the filler. Ductility improvement of some superalloy substratesis achieved at temperatures above about 80% of the alloy's meltingpoint. Similarly, a chill fixture could optionally be used forparticular applications, which in combination with the precision heatinput of an energy beam can minimize stresses created in the material asa result of the melting process. Furthermore, the processes describedherein may negate the need for an inert shielding gas, althoughsupplemental shielding gas may be used in some applications ifpreferred. If a filler material 44 is used, it may be pre-heated in someembodiments.

Flux materials which could be used include commercially available fluxessuch as those sold under the names Lincolnweld P2007, Bohler SoudokayNiCrW-412, ESAB OK 10.16 or 10.90, Special Metals NT100, Oerlikon OP76,Sandvik 50SW or SAS1. The flux particles may be ground to a desiredsmaller mesh size range before use. Flux materials known in the art maytypically include alumina, fluorides and silicates. Embodiments of theprocesses disclosed herein may advantageously include metallicconstituents of the desired cladding material, for example chromeoxides, nickel oxides or titanium oxides. Any of the currently availableiron, nickel or cobalt based superalloys that are routinely used forhigh temperature applications such as gas turbine engines may be joined,repaired or coated with the inventive process, including those alloysmentioned above.

Other variations may provide the heat for melting through the feedmaterial rather than or in combination with an energy beam. For example,the wire or strip feed material 44 of FIG. 2 may be energized to createan arc under the layer of powder and flux, with the wire being amaterial that is readily available in extruded form (i.e. not asuperalloy material) and the powder including the other alloyingelements necessary to form a desired superalloy composition in thecombined melt pool. Alternatively, the powder and flux may be selectedto be conductive such as to facilitate an electro-slag welding processeffective to form the layer of superalloy cladding material. In yetanother embodiment, flux powder mixed with superalloy powder materialmay be fed to a superalloy substrate using conventional plasma arccladding equipment, optionally with a chill fixture. The substrate, feedmaterial and/or powder may be preheated in various embodiments. Becausethe degree of precision of the heat input is higher with the energy beam(±1-2%) than with an electrode (±10-15%), it may be desirable to utilizethe energy beam for more than half of the total heat input. The beamenergy may lead the submerged arc or electroslag process to initiate apreliminary melt pool with minimum dilution from the substrate, then thesubmerged arc or electroslag contribution can add to the volume ofdeposit without significant further substrate impact, thereby minimizingdilution effects.

In accordance with other embodiments, mixed submerged arc welding fluxand alloy 247 powder was pre-placed from 2.5 to 5.5 mm depths anddemonstrated to achieve crack free laser clad deposits after final postweld heat treatment. Ytterbium fiber laser power levels from 0.6 up to 2kilowatts have been used with galvanometer scanning optics makingdeposits from 3 to 10 mm in width at travel speeds on the order of 125mm/min. Absence of cracking has been confirmed by dye penetrant testingand metallographic examination of deposit cross sections. It will beappreciated that alloy 247 falls within the most difficult area of thezone of non-weldability as illustrated in FIG. 6, thereby demonstratingthe operability of the invention for a full range of superalloycompositions, including those with aluminum content of greater than 3wt. %.

It is appreciated that the advantages of utilizing powdered fluxmaterial when repairing a superalloy substrate are realized whether ornot an additive cladding material is deposited. Surface cracks in asuperalloy substrate may be repaired by covering the surface withpowdered flux material, then heating the surface and the flux materialto form a melt pool with a floating slag layer. Upon solidification ofthe melt pool under the protection of the slag layer, a clean surfacewith no cracks will be formed.

Laser energy may be applied across a surface area by using a diode laserhaving a generally rectangular energy density. Alternatively, it ispossible to raster a circular laser beam back and forth as it is movedforward along a substrate to effect an area energy distribution. FIG. 5illustrates a rastering pattern for one embodiment where a generallycircular beam having a diameter D is moved from a first position 74 to asecond position 74′ and then to a third position 74″ and so on. Anamount of overlap O of the beam diameter pattern at its locations of achange of direction is preferably between 25-90% of D in order toprovide optimal heating and melting of the materials. Alternatively, twoenergy beams may be rastered concurrently to achieve a desired energydistribution across a surface area, with the overlap between the beampatterns being in the range of 25-90% of the diameters of the respectivebeams.

It will be appreciated that the use of powdered material facilitates thedeposition of functionally graded materials, where the composition ofthe deposited material varies across time and space. For example, thealloy composition may vary from an interior wall to an exterior wall ofa product, or from within a product to near it's surfaces. The alloycomposition may be varied in response to anticipated operatingconditions requiring different mechanical or corrosion resistanceproperties, and with consideration of the cost of the materials.

While various embodiments of the present invention have been shown anddescribed herein, it will be obvious that such embodiments are providedby way of example only. Numerous variations, changes and substitutionsmay be made without departing from the invention herein. Accordingly, itis intended that the invention be limited only by the spirit and scopeof the appended claims.

The invention claimed is:
 1. A method comprising: providing a feedmaterial comprising a sheath consisting essentially of pure nickelcontaining a powdered core material, the powdered core materialcomprising powdered metal material and powdered flux material; meltingthe feed material onto a substrate to form a melt pool; allowing themelt pool to cool to form a layer of clad material of a desiredcomposition covered by a layer of slag; further comprising: selectingthe powdered metal and powdered flux materials to comprise elements thatcomplement the sheath to form the clad material as a desired superalloymaterial when melted onto the substrate; and selecting the sheath andpowdered core materials such that the clad material desired compositionis a superalloy composition that lies beyond a zone of weldability whendisplayed on a graph of superalloys plotting titanium content versesaluminum content, wherein the zone of weldability is upper bounded by aline intersecting the titanium content axis at 6 wt. % and intersectingthe aluminum content axis at 3 wt. %.
 2. The method of claim 1, furthercomprising: selecting the desired composition of clad material toinclude titanium; providing a shielding gas comprising carbon dioxide oroxygen during the step of melting; and providing the powdered corematerial to comprise titanium to compensate for a loss of titanium dueto reaction with the oxygen or carbon dioxide and subsequentvaporization during the melting step.
 3. The method of claim 1, furthercomprising heating the feed material with laser energy during the stepof melting.
 4. The method of claim 1, further comprising heating thefeed material with an electrical current during the step of melting. 5.The method of claim 1, further comprising pre-heating the feed materialwith an electrical current, then melting the pre-heated feed materialwith laser energy during the step of melting.
 6. The method of claim 1,further comprising providing the powdered metal material and thepowdered flux material to have an overlapping mesh size range.
 7. Themethod of claim 1, further comprising providing the powdered metalmaterial and the powdered flux material to have the same mesh sizerange.
 8. The method of claim 1, further comprising supplying asupplemental powdered metal material to the melt pool during the step ofmelting.
 9. The method of claim 1, further comprising processing thepowdered flux material to comprise at least one of the group of chromeoxides, nickel oxides, titanium oxides, and titanium carbides.